ERROR LOADING WSDL

Hi,
When i am trying to deploy the wsdl in the SOAP UI Tool , i am getting the following error. The web service id developed using .Net technology and requires NTLM authentication . Even though i am providing all the authentication details,still i am facing the error.

[ERROR]

org.apache.xmlbeans.XMLException.org.apache.xmlbeans.XMLException:error:Unexpected end of file after null.

[/ERROR]

what can be the cause? How can i fix this error?

I am using Soap Ui 4.0.0

Thanks in advance